Re: microstep accuracy was what comprises as step

Hi,

Actually microstepping does improve positional accuracy within
certain constraints. As mentioned, a typical motor has a +/- 5% non-
accumulative error. This means any step is within a 10% error band of
where you would expect it to be. This alo happens to mean a motor has
an overall accuracy of 1 part out of 2,000 or 1/10 of a full step.

Many new "square" motors are linear (sin/cos angle vs. motor
position) within 1%. This means the measured position is within 1% of
where it is predicted to be. Paricularly good motors in this respect
are the Vexta PK series, Sanyo Denki 103 series and PacSci M31 series
among others.

What limits the usefulness of this accuracy is the amount of torque
required to move the motor off-position. At 10 microsteps/ step this
is about 10% of the motor's holding torque. At 100 microsteps/step it
would take 1% of the holding torque to move it off position 1
microstep.

Mariss

--- In CAD_CAM_EDM_DRO@y..., "ballendo" <ballendo@y...> wrote:
> Dave,
>
> Unless the motor, drive, and machine are matched you DO NOT get
> increased "positional accuracy" from a microstep drive.
>
> What you get is smoothness. Quietly. Positional accuracy of any
> stepper is limited by the construction of the motor, which is
> typically rated as expecting any FULL step to be within 3% of
where
> it "should" be... And many motors are 5%.
>
> Hi-end microstepper systems used in um positioning are carefully
> designed, made, matched, and integrated all the way through the
> design process. Just changing the sin/cos values of the winding
> current(s) to make smaller steps is not enough. Magnetic position
is
> not always(often) the same as the mathematical model would have us
> believe.
>
> You're damp, but so are a lot of others on this subject<G>.
>
> Hope this helps,
>
> Ballendo
>
>
> --- In CAD_CAM_EDM_DRO@y..., "dave_ace_me" <davemucha@j...> wrote:
> <Snip>
> >If I am not mistaken, the Gecko uses a micro step and breaks that
> >into 10 parts of a step or 1/10 step per pulse. This would mean
> >that it would drive a stepper 10 times slower, but with 10 times
the
> >positioning accuracy of a full step drive.
> <snip>
> > leadscrew revolutions per stepper revolution, but by using the
> Gecko,the same leadscrew speed would be achieved, AND the same
> positional accuracy would be had.
> <snip>
> >Am I right on or all wet ? (or maybe just a little damp?)
> >
> >
> > Dave